JP5359103B2 - Charge / discharge control method for power storage device - Google Patents

Description

  The present invention relates to a charge / discharge control method for a power storage device, and more particularly to a charge / discharge control method for a power storage device configured by connecting different power storage media having different discharge behaviors in parallel.

  For example, when a power storage device is configured by connecting an electric double layer capacitor and a storage battery in parallel as the power storage medium, the charge / discharge behavior (change in terminal voltage due to charge / discharge) varies depending on the charge storage principle and storage capacity. ) Is very different. That is, the terminal voltage during charging / discharging of the electric double layer capacitor greatly changes, but the terminal voltage fluctuation of the storage battery is smaller than that of the electric double layer capacitor. For this reason, when the electric double layer capacitor and the storage battery are connected in parallel and used, the electric double layer capacitor is always charged by the charge from the storage battery during charging, and the electric double layer capacitor is always in a fully charged state. The quick charge which is one of the characteristics of the capacitor is not performed. In addition, rapid charging from the storage battery to the electric double layer capacitor increases the depth of discharge of the storage battery and shortens the life of the storage battery.

Note that Patent Document 1 has been disclosed for connecting different types of power storage media in parallel. This document describes a dedicated lead battery that replenishes only the self-discharge current for the self-discharge property of the electric double layer capacitor for the purpose of reducing the size and weight of the power supply device for the vehicle and extending its life. Is described.
Japanese Patent Application Laid-Open No. 9-247850, especially FIG.

  As represented by Patent Document 1, the terminal voltages of the electric double layer capacitor and the lead storage battery become the same after a long time. When charging in this state, there is no difference between the terminal voltage of the electric double layer capacitor and the lead storage battery, so the charging current of the electric double layer capacitor cannot be increased, and eventually the charging current of the electric double layer capacitor decreases. Since the charging current of the storage battery increases, the life of the lead storage battery is not extended. In addition, since the resistor R1 connected between the electric double layer capacitor and the lead storage battery and the diode + R2 connected in parallel with the resistor R1 are connected in parallel, the resistance value of the resistor R1 must be larger than the resistance value of the diode + R2. For example, current flows from the lead storage battery to the electric double layer capacitor via R1, and the effect of the diode is reduced. In order to prevent this phenomenon, the resistance value of the resistor R1 is increased. However, since the resistance value is increased, the loss due to the resistor R1 increases.

  When an electric double layer capacitor and a storage battery are connected in parallel as described above, since the voltage fluctuation range of the storage battery is small, the electric double layer capacitor is charged from both the power source and the storage battery, and the merit of connecting in parallel Less. Therefore, conventionally, a step-up / step-down chopper circuit is provided for both the electric double layer capacitor and the storage battery, and the characteristics of the electric double layer capacitor and the storage battery are effectively used by controlling each of them. For this reason, two step-up / step-down chopper circuits are required, which causes a problem that the apparatus is expensive and the control is complicated.

  An object of the present invention is to provide a charge / discharge control method that enables charge / discharge in a power storage device in which different types of power storage media having different charge / discharge behaviors are connected in parallel.

The present invention is a power storage device configured to power storage medium change is large different charge and discharge time of the terminal voltage is small power storage medium and the terminal voltage change of the charging and discharging behavior in parallel connection,
A charge / discharge suppression unit is provided only between the power storage medium and the power source where the change in the terminal voltage is small, and this charge / discharge suppression unit is a series circuit of a diode and a charge suppression resistor provided in the forward direction for charging, Consists of a series circuit of a discharge suppression resistor and a switch body connected in parallel with the series circuit, and when the power storage medium connected in parallel is charged, the switch body is opened, and when the power storage medium connected in parallel is discharged In the charge / discharge control method of the power storage device configured to close the switch body ,
Examples different power storage medium of charging and discharging behavior, are connected in parallel蓄battery with an electric double layer capacitor, the electric double layer capacitor (internal resistance × discharge current), the battery ((internal resistance + discharge suppression (Resistance) × Discharge current) .

The present invention is characterized in that the discharge current of the electric double layer capacitor and the storage battery is monitored, and when the electric current drops below a certain current, the switch body is opened to continue the discharge only on the electric double layer capacitor side . Is.

As described above, according to the present invention, the charging / discharging suppression unit is provided only between the power storage medium and the power source, in which the terminal voltage change during charging / discharging is small, the switch body is opened when the power storage medium is charged, By controlling to close the body, it is possible to charge and discharge a large current with a power storage medium with a large change in terminal voltage, charge and discharge for a long time with a power storage medium with a small change in terminal voltage, and power with different charge and discharge behavior The characteristics of the storage medium can be used effectively. In addition, when charging the power storage medium, charging from a power storage medium with a small terminal voltage change during charging / discharging, such as a storage battery than a diode, to a power storage medium with a large terminal voltage change, such as an electric double layer capacitor, is prevented. In addition, since the charging current is suppressed by the resistor provided in series with the diode, the life of the storage battery can be extended.
Moreover, at the time of discharge, it is discharged from the power storage medium connected in parallel. However, since the discharge current is suppressed by the resistance from the power storage medium such as a storage battery in which the change of the terminal voltage at the time of charging and discharging is small, it is excessive. Discharge current is prevented.

1 and 2 are equivalent circuits of a power storage device according to an embodiment of the present invention. FIG. 1 shows an equivalent circuit during charging, and FIG. 2 shows an equivalent circuit during discharging. Here, the case where the electric double layer capacitor 2 and the storage battery 3 such as lead are used as the different power storage medium having different voltage fluctuation ranges during charging and discharging is shown. 1 is a power supply for supplying power to a load, 4 is a charge / discharge suppression unit, and this charge / discharge suppression unit 4 is a series circuit of a diode D and a charge suppression resistor R1 provided in the forward direction for charging the storage battery 3. And a series circuit of a switch body SW including a discharge suppression resistor R2 and an IGBT or the like connected in parallel with the series circuit. In the power supply 1, Vs is a power supply voltage, and Rs is a power supply resistance. Further, Cc of the electric double layer capacitor 2 is a capacitance of the electric double layer capacitor, and Rc is an electric double layer capacitor equivalent internal resistance. Further, Eb of the storage battery 3 is a storage battery capacity, and Rb is a storage battery equivalent internal resistance.

When the voltage of the power source 1 becomes higher than the terminal voltage of the electric double layer capacitor 2, the power storage device enters the charging mode. At this time, the switch body SW is in an open state, and the terminal voltage of the storage battery 3 is designed to be higher than the terminal voltage of the electric double layer capacitor 2 during the previous discharge as described later. Thereby, the charging current Ib to the storage battery 3 is suppressed by the charging suppression resistor R1 to charge the storage battery 3, but the charging current Ic to the electric double layer capacitor 2 is not suppressed and from the terminal voltage of the storage battery 3 Since the terminal voltage of the electric double layer capacitor 2 is low, the electric double layer capacitor 2 is charged with a large current for a short time.
After charging, the charging current from the storage battery 3 to the electric double layer capacitor 2 is blocked by the diode D and does not flow because the switch body SW is opened.
On the contrary, since the charging current from the electric double layer capacitor 2 to the storage battery 3 flows, the terminal voltage of the electric double layer capacitor 2 becomes equal to the terminal voltage of the storage battery 3.
Therefore, if the rated voltage of the electric double layer capacitor 2 is made higher than the terminal voltage of the storage battery 3, the electric double layer capacitor 2 will not always be fully charged, and the resistance value of the suppression resistor R2 is increased. However, no current loss occurs during charging.

  Next, when the terminal voltage of the power source 1 is lower than the terminal voltage of the power storage medium, a discharge mode for discharging the energy stored in the power storage device is set. In this case, the control device detects a voltage drop and places the switch body SW in a closed state. Thereby, the current Ic from the electric double layer capacitor 2 flows out to the power supply side without being suppressed, but the discharge current Ib from the storage battery 3 is discharged through the switch body SW while being suppressed by the discharge suppression resistor R2. . That is, the electric double layer capacitor 2 is charged / discharged by the large current Ic, but the storage battery 3 is gradually discharged over a long period of time, and the features of both power storage media are effectively utilized.

As described above, the charging current from the storage battery 3 to the electric double layer capacitor 2 does not flow after charging.
Further, the terminal voltage of the electric double layer capacitor and the storage battery at the time of discharging is Vc + Ic × Rc = (Rb + R2) × Ib + Vb. (However, Vc is the electric double layer capacitor terminal voltage and Vb is the storage battery terminal voltage.)
From this, the following becomes possible.
<When the discharge current stops suddenly>
When the discharge current stops suddenly, Ic = Ib = 0, the terminal voltage of the electric double layer capacitor is Vc, and the terminal voltage of the storage battery is Vb. That is, by designing so that Ic × Rc is larger than (Rb + R2) × Ib, the terminal voltage Vc of the electric double layer capacitor can be made lower than the terminal voltage Vb of the storage battery. In this terminal voltage relationship, since the switch body SW is opened at the time of charging, the state of Vc <Vb is maintained after the end of discharging, and a large charging current can be supplied to the electric double layer capacitor at the next charging. .
<When discharge current decreases slowly>
As the discharge currents Ic and Ib slowly decrease, the voltage Vc of the electric double layer capacitor and the voltage Vb of the storage battery have the same potential. For this reason, the discharge current is monitored, and the switch body SW is opened in the middle of the discharge when the current is equal to or less than a certain current, and control is performed such that Vc becomes lower than Vb by discharging only the electric double layer capacitor.

The equivalent circuit diagram at the time of charge which shows embodiment of this invention. The equivalent circuit figure at the time of discharge of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Power supply 2 ... Electric double layer capacitor 3 ... Storage battery 4 ... Charge / discharge suppression part

Claims (2)

A different charging and discharging time of the electric power storage device configured by parallel connection of power storage medium change is large in change is small power storage medium and the terminal voltage of the terminal voltage of the charge-discharge behavior,
A charge / discharge suppression unit is provided only between the power storage medium and the power source where the change in the terminal voltage is small, and this charge / discharge suppression unit is a series circuit of a diode and a charge suppression resistor provided in the forward direction for charging, Consists of a series circuit of a discharge suppression resistor and a switch body connected in parallel with the series circuit, and when the power storage medium connected in parallel is charged, the switch body is opened, and when the power storage medium connected in parallel is discharged In the charge / discharge control method of the power storage device configured to close the switch body ,
Examples different power storage medium of charging and discharging behavior, are connected in parallel蓄battery with an electric double layer capacitor, the electric double layer capacitor (internal resistance × discharge current), the battery ((internal resistance + discharge suppression The charge / discharge control method for a power storage device, characterized in that it is greater than (resistance) × discharge current) . The discharge current of the electric double layer capacitor and the storage battery is monitored, and the switch body is opened when the electric current drops below a predetermined current to continue the discharge only on the electric double layer capacitor side. Charge / discharge control method for power storage device.

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